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Beginner Tutorial 9

An interchangeable lens system camera comes with a useful kit lens, but when you come to buy additional lenses you will want to know the different types available, which shooting scenarios they are useful for and what the figures in their spec – and written on the front – mean. Here is a handy guide…

9

A quick guide to lenses

The LUMIX G6 with one of its ‘kit lens’ options

A very important part of your system, affecting the quality as well as the artistic look of your photographs, is your choice of lens.

With compact cameras, it is largely lens quality that sets the better models apart from the more modest ones. A compact’s lens is integral to its construction and cannot be changed, whereas the system camera buyer has the freedom of interchangeable lenses and can influence the quality and creativity of their photography accordingly.

For the system camera user, it is usual that your first option is the ‘kit lens’ that came in the package, often a general-purpose zoom. This will suffice to get you up and running, but as your skills develop you will soon find yourself wanting to try different shooting scenarios that may require more specialised lenses. So, as there are so many types of lenses available – ranging in price from a few hundred pounds to many thousands – how do you know what to look for?

What are the different types of lens?

Lenses are broadly grouped according to the angle of view they produce on the camera’s image sensor:

Ultra-wide-angle

Wide-angle

Standard

Telephoto

Super telephoto

There are also sub-groups within these categories (fixed focal length, zoom, macro) and we will return to lenses in later tutorials. But as a beginner’s guide, let’s start with the ultra-wide-angle lens. As its name suggests, this will give a very wide viewing angle that enables the camera to capture landscape vistas and wide-open spaces, as well as large groups of people – or very tall buildings. At the opposite end of the scale, a super telephoto lens captures a very narrow angle while magnifying distant subjects, making them appear much closer to the camera than they actually are:

As well as the diagram, look at the thumbnail images showing the subject appearing closer and closer as the angle of view narrows. With lenses categorised into the groups we have mentioned, a more precise way of knowing the angle of view is often required – this is where ‘focal length’ comes in.

Lenses and focal length

Focal length is the distance from the sensor to the point where light rays captured by the lens converge – known as the focal point.The reason focal length is important is that by designing lenses that move the focal point within the barrel, it is possible to precisely widen or narrow the angle of view, so creating a wide-angle or telephoto lens. Lenses with a moving focal point are called zooms, whereas those with a fixed focal point are called ‘fixed focal length’ or ‘prime’ lenses.

The focal length gives us a standard measurement that is quoted on all lenses, and we can use this to calculate their angle of view.

This telephoto zoom lens has a 35-100mm focal length

This wide-angle prime lens has a 14mm focal length

Look again at the diagram and thumbnails; notice the focal length figures, in millimetres, relating to each angle of view. The smaller the figure, the wider the view; the larger, the closer the image appears. As you can see, by knowing a lens’ focal length (and therefore its angle of view), we have an idea how much of a scene will be captured in the image.

A good tip to help you gauge angle of view is that a 50mm focal length captures a view very similar to the human eye. For this reason, lenses close to 50mm fall in to the ‘Standard’ category.

Focal length and the crop factor

When comparing lenses, it is also important to be aware of your camera’s ‘crop factor’. The focal lengths in our diagram relate to a 35mm film camera, as this was the standard format before digital and most experienced photographers are familiar with that system, making it the standard basis for comparison. However, most digital cameras use an image sensor smaller in size than 35mm film, meaning that when comparing the focal lengths of today’s lenses, you need to take into account the cropping effect.

The ‘crop factor’ is quoted for all interchangeable lens system cameras, to make it easier to compare with ‘full-sized’ 35mm. LUMIX G cameras have a crop factor of 2x, meaning that the focal length quoted on their Micro Four Thirds lenses (MFT is the Panasonic/Leica system) should by multiplied by two to give the same angle of view as 35mm, so 14mm MFT lens focal length = 28mm equivalent. Other manufacturers’ crop factors include 2.7x, 1.6x and 1.5x, so when comparing lenses, don’t overlook this factor!

What do the other lens numbers mean?

You will notice other numbers given on lenses. These are also important indicators of how a lens will perform:

The lens ring size [ø37mm] is the diameter of the outer lens thread, required for fitting accessory filters or conversion lenses.

[14-42] Focal length Range (mm) is given as a range (from wide-angle to telephoto) in the case of a zoom lens.

The maximum lens aperture/f number (given as a ratio, 1:3.5) tells you how much light the lens lets in; the smaller the ratio, the ‘brighter’ the lens, as it can let in more light. Also, the brighter the lens, the greater the potential to use fast shutter speeds. It is normal for the maximum lens aperture to decrease at the telephoto end, so zoom lenses often show the aperture ‘range’, as in 1:3.5 – 5.6.

Focal Length Range (mm)

The Minimum to Maximum Focus Distance [0.2m/0.66ft – ∞]. The minimum distance is important to let you know how close you can get to your subject while still being within the lens’ range of focus.

Image Stabilisation

Many great shots can be spoiled by blurring due to hand-shake. This is especially difficult to stop with telephoto lenses or when shooting at night, as shown. A good way to reduce it is to opt for a lens with some form of Optical Image Stabilisation (IS or OIS). Such lenses use a gyroscopic sensor and motor to counteract small camera movements, therefore, the subject stays in the same place on the sensor and is captured without blur – as in the second example:

Image blur caused by camera shake

Optical Image Stabilisation can counteract blur

The more you zoom in on your subject, the more noticeable camera shake blur becomes. So for telephoto lenses, image stabilisation is generally regarded as an essential part of their spec. The only time you would ever need to switch off the stabiliser is if you are shooting with a tripod, or resting the camera on a solid surface.

The LUMIX Advantage

The advantage of LUMIX Micro Four Thirds lenses is they were designed from conception for digital use. Smaller and lighter than conventional lenses, they also deliver light at a perpendicular angle to the sensor, reducing distortion and more efficiently using available light.

Such high-end performance belies their compact size – and with the strict manufacturing ethos of both Panasonic and Leica adopted at factory level, optical quality is assured. The largest range available for digital interchangeable lens cameras is that offered by MFT manufacturers such as Panasonic – which is also the most experienced in mirrorless system camera design: